FIG. 8 is a diagram illustrating a configuration of a test system 100 of an engine E using a dynamometer DY. The test system 100 includes: a dynamometer DY connected to an engine E serving as a test piece via a shaft S; a throttle actuator 110 and an engine control device 120 for controlling an output of the engine E; and an inverter 130 and a dynamometer control device 140 for controlling an output of the dynamometer DY. With the test system 100, the torque and speed of the dynamometer DY are controlled by using the dynamometer control device 140, while controlling a throttle opening degree of the engine E by using the engine control device 120, whereby the durability, fuel efficiency and exhaust gas purification performance of the engine E are evaluated. With the test system 100, in some cases, the moment of inertia of the engine E is measured prior to performing the test to evaluate the performance as described above, and is utilized as a control parameter in torque control and speed control in relation to the dynamometer control device 140.
Patent Document 1 discloses a method for estimating the moment of inertia of the engine E by using a device configuring the test system 100 as described above. With the method of Patent Document 1, the dynamometer control device 140 performs excitation control of the torque acting on the shaft S, while maintaining the rotation speed of the engine E constant by using the engine control device 120. Outputs of the shaft torque sensor 160 and the rotation speed detector 150 under such excitation control are acquired by way of the arithmetic device 170, and a value of the moment of inertia of the engine E is estimated by using the data acquired. In general, the engine E has a mechanical loss depending on the rotation speed. In contrast, according to the method of Patent Document 1, the moment of inertia of the engine E is estimated while maintaining the rotation speed substantially constant, therefore, such a mechanical loss does not need to be taken into account.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2006-300683